RU2402502C9 - Concrete mixture - Google Patents

Abstract

FIELD: chemistry. ^ SUBSTANCE: invention relates to modified concrete mixtures with special properties. The concrete mixture contains cement, aggregate, modifier and water. The mixture also contains polyhydrosiloxane and ground rock. The cement used is portland cement, the modifier is microsilica and/or flue ash and plasticising agent, and the ground rock is ground quartz sand or ground limestone or ground volcanic rock, with the following ratio of components, wt %: cement 7-20; aggregate 60-85; modifier 0.01-5.50; polyethylhydrosiloxane 0.002-0.010; ground rock 2-15; water - the rest. The ground rock has particle size of not more than 1300 mcm. ^ EFFECT: higher concrete strength. ^ 2 cl, 2 tbl

Description

The invention relates to modified concrete mixtures with special properties.

Concrete mixtures are known, including cement, aggregates, plasticizers and water (V.G. Batrakov. Modified Concretes. M .: Stroyizdat, 1990). The disadvantage of these mixtures is that the resulting mixtures, having increased mobility and segregation resistance, but not long-term storage, provide concrete or low strength with low heat or high strength, but with high heat, which contributes to the formation of cracks in structures due to increased thermal gradient.

Closest to the proposed concrete mixture, the technical essence is concrete mixture, which includes cement (Portland cement), aggregates (sand and gravel), water and an organo-mineral multicomponent modifier, including dispersed silica-containing waste from the production of silicon-containing alloys, fly ash and superplasticizer ( RU 2096372, publ. 11/20/1997).

The disadvantage of this mixture is that with a decrease in the delamination of the mixture and an increase in the strength of concrete at the age of 28 days, the mixture is not sufficiently preserved and the heat of concrete is low during cement hydration.

The technical task is to provide a set of properties: increasing the shelf life and reducing the delamination of the concrete mixture and heat dissipation of concrete while increasing the strength of concrete at the age of 28 days or more.

The problem is solved in that in the concrete mixture, including cement, aggregate, modifier and water, polyethylene hydrosiloxane and ground rock are additionally added, while Portland cement is used as cement, as silica fume and / or fly ash and plasticizing additive as a modifier either silica fume and / or an expanding component and a plasticizing additive, and as ground rock - crushed quartz sand, or ground limestone, or ground volcanic rock in the following ratio ENTOV in wt.%:

Cement 7-20 Aggregate 60-85 Modifier 0.01-5.50 Polyethyl hydrosiloxane 0.002-0.010 Ground rock 2-15 Water Rest

In this case, the ground rock is used preferably with a particle size of not more than 1300 microns.

For the preparation of concrete mixtures, the following materials were used:

Cement: Portland cement, grade ПЦ 500 Д0 (GOST 10178) with specific heat output of 7 days - 330 kJ / kg, and of 28 days - 370 kJ / kg

Aggregate:

Sand quartz Mkr = 2.7 (GOST 8736)

Granite crushed stone 5-20 mm (GOST 8267)

Other known aggregates for concrete (expanded clay slag, gravel), preferably fractions of not more than 40 mm, can also be used as aggregates.

Modifier:

Organic-mineral modifier MB-01 (TU 5743-073-46854090-98)

Organic-mineral modifier MB-S (TU 5743-083-46854090-98)

Organic-mineral modifier Embelit (TU 5870-176-46854090-04)

Superplasticizer S-3 (TU 2481-016-00369171-99)

Polyethyl hydrosiloxane: in the form of a silicone emulsion KE 30-04 diluted to 50% concentration (TU2251-035-00209013-2004)

Polyethyl hydrosiloxane can be used in pure form or in an emulsion of a different concentration.

The compositions of the organic-mineral modifiers are shown in table 1.

Table 1 №№ Modifier brand The composition of the modifier,% by weight of the modifier silica fume fly ash expanding component plasticizer one MB 10-50C 45 45 - 10 2 MB 10-01 90 - - 10 3 MB 10-100C - 90 - 10 four Embalite 6-50 46 - 48 6 5 Embalit 8-100 - - 92 8

As an expanding component, a mixture of metakaolin and gypsum gypsum in a ratio of 1: 1 was used. Other expanding components can also be used, for example, on an oxide basis (calcium or magnesium oxide) with sulfoaluminate.

The modifier can be used as a single multicomponent powder product, or each of the above components of the modifier can be introduced into the concrete mix separately.

Ground Rock:

Unactivated mineral powder (GOST R 52129-2003) - ground limestone.

Sand quartz (GOST 2138-91) - ground quartz sand.

Sand from tuff (GOST 22263-76) - ground volcanic rock.

Ground rock may have a particle size of up to 2 mm, but preferably not more than 1300 mm in accordance with the specified GOST.

The preparation of the concrete mixture was carried out in stationary concrete mixers of compulsory action. The sequence of loading materials into a stationary concrete mixer and the duration of their mixing was as follows:

- loading aggregate (crushed stone and sand) with stirring for 10 seconds;

- loading cement and modifier with stirring for 10 seconds;

- loading mixing water and emulsion KE 30-04 with stirring for 100 ... 240 sec.

Further mixing is carried out in a concrete mixer during the transportation of concrete to the construction site.

Three series of concrete mixtures with cement consumption of 250, 350 and 500 kg / m ^{3 were} prepared. In each series, samples are provided with a ratio of components corresponding to the closest analogue (control samples) and corresponding to the proposed technical solution. The compositions of concrete mixtures, the characteristics of mixtures and concrete are presented in table 2. The concrete samples presented in the table 1, 9, 17 correspond to the closest analogue.

The mobility of concrete mixtures was evaluated by cone (OK) sediment (GOST 10181), persistence - by the change in cone (OK) precipitation over time, segregation by water separation (GOST 10181), concrete strength - by testing 10 × 10 × 10 cm cubic samples, solidified under normal conditions (GOST 10180), heat release - by the calorimetric method (GOST 24316).

Considering that the kinetics of heat generation of Portland cement is intense for 7 days from the moment of mixing it with water, and subsequently slows down, in order to compare the intensity of the exothermic process of concrete, the heat generation values of concrete samples were determined at 7 days of age.

From a comparison of the properties of the proposed and known compositions, it can be seen that the introduction of polyhydrosiloxane and ground rock leads to an increase in shelf life without increasing stratification, as well as to a reduction in heat generation, while allowing (in comparison with the prototype) to increase the strength of concrete at the same flow rate cement.

Thus, the invention allows to increase the shelf life of the concrete mixture, to reduce the consumption of cement while ensuring high mobility of the mixture and, as a result, to reduce heat generation with increasing concrete strength.

Claims (2)

1. Concrete mixture, including cement, aggregate, modifier and water, characterized in that it additionally contains polyhydrosiloxane and ground rock, while Portland cement is used as cement, as a modifier is silica fume and / or fly ash and a plasticizing agent or silica fume and / or an expanding component and a plasticizing additive, and as ground rock - crushed quartz sand, or ground limestone, or ground volcanic rock in the following ratio of components, wt.%:
Cement 7-20 Aggregate 60-85 Modifier 0.01-5.50 Polyethyl hydrosiloxane 0.002-0.010 Ground rock 2-15 Water Rest 2. The concrete mixture according to claim 1, characterized in that the ground rock has a particle size of not more than 1300 microns.